Electrical synchronism.



UNITED STATES PATENT OFFICE.

EDWIN F. N ORTHRUP, OF PHILADELPHIA, PEN N SYLVAN IA,ASSIGNOR TO LEEDS AND NORTHRUP COMPANY, OF PHILADELPHIA, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA. I

Specification of Letters Patent.

Patented Feb. 5, 1907.

Application filed October 18, 1906- Sarial No. 339.469.

To all whom it may concern. Be it known that I, EDWIN F. N ORTHRUP a citizen of the United States, residing at Philadelphia, in the county of Philadelphia and State of Pennsylvania, have invented certain new and useful Improvements in Electrical Synchronism, of which the following is a spccification.--

This invention relates to improvements in the synchronizing of dynamos, motors, rotary transformers, and the like, the said invention being characterized by its great simplicity, its a plicability to machines of any size, and by t e fact that the forces which roduce the s chronism also tend to stop t e hunting,

- t ereby rendering the employmentof any tion, and wherein-- mechanical device for this purpose unnecessary.

In many systems hitherto used it has been necessary to employ some such arrangement as a hollow fly-wheel filled with heavy liquid or some other mechanical or elcctromcchan ical device for the purpose of damping out the variation of the moving body from a steady motion. With my invention no such extra means are necessary.

The invention is further characterized by the fact that the synchronizin force acts on the body to be synchronized whether the device is in synchronism or running at a speed above that of synchronism, so that is it not necessary for the device to first get out of synchronism before the synchronizing force begins to act. In other words, there is a force which acts constantly to preserve synchronism, a synchronizing impulse being given at every alternation of the alternating current or multiple thereof.

My said invention may be better understood by reference to the accompanying drawings, which form a partof this specificaing frequency for certain purposeshs, for g example, testing and calibrating electrical instruments and operating vibrating bodies that respond to definite frequency. The frequency being constant, the speed of rotation is also constant, adapting t e apparatus tochronographs and the like, though I do not wish to be understood as limiting it to this or any other single application, for it may be applied also to synchronous telegraphs, and, in fact, to the production of synchronous motion for any useyto which it may be applied. 1

In the arrangement shown in Fig. 1, 1 is a conventional representation of the armaturewim ings of a rotary converter; 2, the regular external alternating-current circuit leading from the alternating-current armature-tors minals 3 4, 8111i in this circuit maybe any suitable load, (represented by the resistance 5.)

The rotar transformer in this case is operated as an inverted rotary and receives the direct current to drive it from the supplymains 6 6. The speed of the rotating element of the machine 1 may be approximately adjusted by rheostat 6, connected in circuit with the driving element, or by other suitable means. Connected also to the alternating-current terminals 3 and 4 is a circuit which includes, essentially, an ohmic resistance and any suitable device for periodic-' all making and breaking the circuit at regulady-recurring intervals, such intervals being preferably equal to or an even multiple of the alterations per second desired. This ohmic resistance is preferably one or more incandescent lampssuch, -for example, as lamp 7 or other body or bodies, the resistance of which decreases as the current through it increases while the contact-maker is preferably, especially in the application of the invention shown, an electrically-driven tuning-fork 8, one of the prongs of which-vibrates between two contacts 9 and 10, though one of said contacts alone may be employed, the body of the tuning-fork being connected to one side of the circuit and the contacts 9 and 10 to the taets 9 and 10, I may connect" a small con denser 11 in shunt around the fork and con-' tacts, as shown. This condenser does not exert any synchronizing effect, but is merely for the purpose stated.

The operation of the parts described is as follows: The tuning-fork is made to vibrate in any of the well-known ways or any other suitable manner at the desired frequency, and'the rotarytransformer or other machine is adjusted by varying the torque of the driving-motor to have a tendency to run at a speed to produce an alternating current of greater frequency than the frequency of the tuningfork; but if the tuning-fork is vihrating it throws the load of the lam 7 or other suitable resistance onthe mac inc 1 that the contact occurs when the wave has thelvalue (1,6, 0, or d, a current will flow through lamp 7, which will be roportional to the instantaneous height of t e wave at a t, &c. The machine 1 will now receive a load each time contact occurs at 9 or 10, which will tend to stop a further increase cf s eed If the motor element is adjusted to rive the generator element at a speed considerably in excess of synchronism, then the height of the wave at the instant of contact will be required to be still greater to produce the necessary retarding effect.v :In other words, the retarding effect or synchronizingload will increase in pro ortion as the ma chine 1 tends to run a ove the s eed of synchronism. When the driving orce of said machine varies or the load thrown on i the alternator is varied, the phaserelation of l the emplo' 6a -with increasing current through it, thereby the alternating wave and the making of contacts 9 1O varies in a similar manner. The synchronizing force thus automaticall increases and diminishes to care for a ten ency to a varying speed. The speed is thus held constant, and the apparatusholdsin synchronism unless the variations of the driving force or the loads thrown on the machine 1 exceed the magnitude of the greatest possi-' greatly strengthening the synchronizing orce. By usin such a resistance the nearer the points a b c, 0., approach the crest'of the waves, 2, at the mstances of contact at 7 to receive current, or, in other words, the

' greater the phase displacement between the alternating current and the tuning-fork the stronger becomes the force to damp down this variation. useful function of indicating by its bright- The lamp 7 also serves the ness the phase alterations of the alternating current with respect to the periodic contacts when the driving force varies. When the driving force tends-to run the machine 1 at exact synchronism, the contacts occur when the current is'passing through zero and the lamp burns very dim. When the driving force increases, contacts occur when the waves approach a maximum'and the lamp 7 burns brightly. Thus an inspection of the lamp. tells how to adjust, the rheostat in the direct-current circuit driving the apparatus. If the apparatus ass out of synchronism,

the lamp varies in rightness in-an irregular manner, and this plainly indicates that the synchronism is destroyed. With the driving force iroperly adjusted if the apparatus is forcibly thrown out of synchronism it will return to synchronism in from two to five seconds.

In Fig. 3 I have shown an arrangement of the apparatus in which the local synchronizing-clrcuit includes the lamp 7; but the tuning-fork is connected to the generator -1 1 through a static transformer 12. I have also shown in this figure means comprisin an electromagnet 13 and make and-br'ea contact 14,connected in circuit therewith for operating the tuning-fork. The condenser 15. is for the purpose merely of preventing s arking at the contact 14 and is usually less than one-tenth M. F. A telephone '16, connected around a resistance '17 in the local iniicate the state of the synchronisml When the apparatusis outof synchronism, I

the telephone emits sound-beats which lengthen as the apparatus gets more nearly into synchronis'm, and the sound becomes a steady hum when synchronism is attained.

IIO

Obviously in view of the indicating quality of the lamp 7 it is not essential to-use'this telephone; but in some cases itmaybe de-- sired.

It will also be understood that the resistance-forming the synchronizing-load may be varied to meet the demands imposed by V- riations in the size of the machines tobe syn chroni'zed. For'example, a single lamp, as

herein illustrated, of from sixteen to thirtyj two 0. P. 'is suflicient for small rotsry-converters-sa'y of one-eighth H. P. or therea Having thus described my invention, what I claim is-- v 1. The, combination with one'o'r more coils with the period of said load-varying means by the load of said resistance.

. 2. The combination with one or more coils arranged to develop a periodically-varying electric current, of a circuit including said coils and a synchronizing ohmic. resistance which decreases as the current through it increases, means to vary the load of said resistance on said coils at regular intervals the natural frequency of which is less than the natural frequency of the said electric current, the latter being damped down to synchronism with the period of said load-varying means by the load of said resistance.

- 3. The combination with one or more coils arranged to develop a periodically-varying J electric current, of a circuit including said coils and a synchronizing ohmic resistance which decreases as the current through it increases, means to vary the load of said resistance on said coils at unvarying intervals, once for each electric impulse ,developed by said coilsor multiple thereof, the natural frequency of which intervals is less than the natural frequency of the said electric current, the latter being damped down to synchronism with the period of said load-varying means by the load of-said resistance.

4. The combination with a rotary alternating-current generator, of a circuit including the armature-coils of said generator and a synchronizing ohmic resistance which decreases as the current through it increases, means to' vary the load of said resistance on said coils at unvarying intervals once for each alternating-current semicycle ,or multiple thereof developed by said generator the natural frequency of which intervals is less than the natural frequency of the said generator, the speed of the latter being damped down to synchronism with the period of said loadvary'ing means by the load of said resistance.

5. The combination with one or more coils arranged to develop a periodically-varying electric current, of a circuit including a synchronizing ohmic resistance inductively connected to said coils, means to vary the load of said resistance on said coils at regular intervals the natural frequency of which is less than the natural frequency of the said electric current, the latter being damped down to synchronism with the period of said leadvarying means by the load of said resistance.

6. The combination with a rotary alternating-current generator, and means to. drive the same, of an external working circuit connected to the armature-terminals of said generator, a synchronizing-circuit connected to the same terminals of said generator with said working circuit and including a synchronizing resistance comprising an incandescent lamp to act as a load on said generator, a contact device comprising a tuning-fork arranged to make and break the electrical continuity of said circuit at unvarying intervals the natural period of which is greater than that of the current developed by said generator, the said load being thrown on said generator once for every semicycle or multiple thereof developed by said generator and act ing to damp the speed of the generator down to synchronism with the periodicity of said tuning-fork.

7. The combination with a rotary alternating-current generator and means to drive the same, of an external working circuit connected to the armature-terminals thereof, a

transformer having its primary connected to said armature-terminals, a synchronizingcircuit including the secondary of said transformer and a synchronizing resistance comprising one or more incandescent lamps to act as a load on said generator, a contact device comprising a tuning-fork arranged to make and break the electrical continuity of said circuit at unvarying intervals the natural period of which is greater than that of the current developed by said generator, the said load being thrown on said enerator once for every semicycle or multip e thereof developed by said generator and acting to damp the speed of the generator down to synchronism with the periodicity of said tuning-fork.

In testimony whereof I affix my signature Witnesses ERNEST Ri'JBEN, GEORGE LACY. 

